Receiver magnets are used in phone receivers, including in mobile phone receivers. The receiver magnet can be used to drive the coils to make the receiver work, thereby operating a speaker in the phone. Receiver magnets can be prone to corrosion that can result in degraded acoustic performance, for example, because of changed size and properties of the magnet itself, and/or because of smaller particles formed as the magnet corrodes. These particles can interfere with other components in the receiver, such as the coils, as they move. This can, for example, produce an undesirable “hissing” noise at the speakers or otherwise degrade audio quality. Hence, there is a need for receiver magnets to be corrosion resistant. Other magnets including rare earth magnets, used in acoustic or other applications, can also benefit from corrosion resistant properties. Corrosion resistant coatings can also be useful in other applications such as electrical contacts.